In one advantages of Hollow Shaft Flat Gearhead motor, it is shown that a motor can be mounted without a coupling.

1. How can such motor absorb load when direct mounting on shaft done?2. Is there any misalignment specification for the Hollow Shaft Flat Gearhead motor? (Declination or Eccentricity)3. Why use stepped load shaft for frequent instantaneous stops or large radial load?

I have found only the installation rule of thumb in the following file for AC Induction Motor Series although I am using DC Motor Series.

Is there a particular motor that you are considering or currently using for your application?

Our hollow shaft flat gearheads have an internal gearing that allows for them to create a higher torque than the motor alone would have been able to produce. Other than the advantage of not needing a coupler, the hollow shaft flat gearheads are designed to prevent saturation of permissible torque even at high gear ratios. A parallel shaft gearhead, on the other hand, will experience torque saturation. Further detail and a picture of the internal gearing of our various gearheads can be found in the reference section of our catalog. Below is a link to this section. Please reference page H-51 (electronically page 3) for the hollow shaft flat gearhead.http://www.orientalmotor.com/products/p ... lation.pdf

This reference also mentions that the gear case has been made more rigid while the gear and bearing outer diameters have been increased. This increase in the diameter allows for a larger thrust load specification for the hollow shaft flat gearheads. Although the value is greater, there is still a limit to the load that the gearhead can handle. There is a table in our catalog which shows the "Permissible Radial Load and Permissible Axial Load" that the gearhead can handle. The table for the hollow shaft flat gearhead of the BLE series is depicted below as an example:

When looking at a dimensional diagram of the hollow shaft flat gearheds, the dimensional tolerance of the hollow bore can be seen. Therefore, it would be recommended to keep your shaft within the provided specifications. You can reference the "Recommended Load Shaft Installation Dimensions" on page D-193 (electronically page 3) of the link below. The table will show the recommended dimensions based on the gearhead part number. http://www.orientalmotor.com/products/p ... Motors.pdf

Lastly, the theory behind the stepped motor shaft is that a larger diameter shaft can better handle the shear force created from an instantaneous stop. When your application is running and you quickly start or stop the load, you are creating a force. Force (measured in Newtons [kg-m/s^2]) is greater when the acceleration rate is larger (meaning your acceleration or deceleration time is shorter). Therefore, an instantaneous stop will cause the most shear force. To go along with this, when creating a stepped shaft, it would be beneficial to round the transition from the larger shaft to the smaller shaft. Reference the "r" in the picture below.

Rounding the transition in the stepped shaft.png (20.09 KiB) Viewed 2133 times

The answer is very well described especially for stepped load shaft explanation, which can be enlarged for some cases because of load considerations, especially the radius requirement for avoiding instant stepping of shaft! Actually my question generally can be applied to any hollow shaft that I will use now and in the future, which is great.

I want to ask one more additional question regading instantaneous stop function of motor I am using (BLH Series motor).

If I am using BLH series motor, how instant is instantaneous stopping of the motor using brake function? I have a need to predict how many turns until the motor really stopped, including force applied by the brakes. What are the brake specifications?

In regards to your follow up question, the time it takes to stop a motor (or the overrun that is witnessed) will be determined by the load condition. This overrun value occurs when the direction input is removed. As a reference, the brushless products have a standard overrun of 2.5 revolutions at the motor shaft. A comparison of the overrun of our products can be seen in the bar graph below:

Overrun Comparison Bar Graph.png (126.79 KiB) Viewed 2092 times

Dynamic braking (referred to as instantaneous stopping) in our brushless DC motors is a function of the driver. The driver brakes the motor by turning off current to the motor and then shorting all phases together, which will create a locked rotor condition. This condition is only active for a very short time so there is no holding torque when you brake the motor using this function. There are no specifications or equations on the instantaneous stopping of the motor, however, when instantaneously stopped, a reference of 0.3 revolutions (rotations) can be used for a no-load state. This value can be referenced from the selection guide linked below. Please reference page 19 (electronically page 5):http://www.orientalmotor.com/products/p ... erview.pdf

In regards to your follow up question, the time it takes to stop a motor (or the overrun that is witnessed) will be determined by the load condition. This overrun value occurs when the direction input is removed. As a reference, the brushless products have a standard overrun of 2.5 revolutions at the motor shaft. A comparison of the overrun of our products can be seen in the bar graph below:

Overrun Comparison Bar Graph.png

Dynamic braking (referred to as instantaneous stopping) in our brushless DC motors is a function of the driver. The driver brakes the motor by turning off current to the motor and then shorting all phases together, which will create a locked rotor condition. This condition is only active for a very short time so there is no holding torque when you brake the motor using this function.

Thank you for the answer.

Is there some current draw specifications using BLH Motor series for instantaneous stop? Maybe something instantaneously higher amps than needed? Maybe it is using some non-mechanical braking? What will happen if current drawn is less than needed when braking starts?

There is no specification shown for the instantaneous stopping of the BLH motor nor our other BLDC products. However, our catalog has a Specification table which shows the rated input current and maximum input current. The BLH motor will draw the current that it needs at any given time and it can draw up to the maximum current value, but will never exceed the maximum current value. Below is the specification page which shows the rated and maximum current values:

BLH Specifications Table.png (180.58 KiB) Viewed 2062 times

Lastly, as long as the Permissible Inertia of the BLH motor is larger than the inertia of the system, there should be no issue for instantaneous stopping of the motor. Please reference the "When instantaneous stop or instantaneous bi-directional operation is performed" section of the table below:

There is no specification shown for the instantaneous stopping of the BLH motor nor our other BLDC products. However, our catalog has a Specification table which shows the rated input current and maximum input current. The BLH motor will draw the current that it needs at any given time and it can draw up to the maximum current value, but will never exceed the maximum current value. Below is the specification page which shows the rated and maximum current values:BLH Specifications Table.png

Lastly, as long as the Permissible Inertia of the BLH motor is larger than the inertia of the system, there should be no issue for instantaneous stopping of the motor. Please reference the "When instantaneous stop or instantaneous bi-directional operation is performed" section of the table below:BLH Permissible Inertia Table.png

Thanks for the answer.

And:

1. Is the rated input current simply proportional to motor speed and motor load? 2. Is there any torque limiter to prevent damage to the BLH motor?

The rated input current is the current at rated speed and rated torque. However, the current that the motor requires at any given time will be dependent on the speed and torque that the motor needs to operate at.

The BLH series does not offer torque limiting, however there is an Overload Protection Function. This function will generate an alarm if there is a load which exceeds the rated torque of the motor for 5 seconds or more. You can reference page 38 of the manual linked below for the overload protection function and other alarms that the BLH product may generate:http://www.orientalmotor.com/products/p ... 130-4E.pdf

The rated input current is the current at rated speed and rated torque. However, the current that the motor requires at any given time will be dependent on the speed and torque that the motor needs to operate at.

Thanks.

Assuming Torque is constant at maximum rated torque, can I predict current input at some fraction of rated speed? For instance (2000/2500)rpm*3.1A=2.48A.